There are many uses for small or even intermediate size unmanned aircraft for performing various types services. Some of these aircraft are preprogrammed to fly a predetermined course and/or they are remotely controlled by radio, etc. An example of this type of aircraft are drones, remotely piloted vehicles for taking photographs, etc. Also it is common now adays to employ model aircraft for training and/or amusement purposes.
Heretofore, it has been customary to use a gasoline engine for driving such airplane. Although such engines are highly developed and reasonably reliable, they do require a considerable amount of servicing and maintenance. This is particularly true with engines having relatively low power ratings for example on the order of 5 or 10 horsepower or less and especially so called fractional horsepower engines. In addition, they also require a considerable amount of special equipment and supplies such as messy gasolines, oils, batteries, etc. Moreover, the gasoline engines are extremely noisy whereby their operation has been banned in many areas.